Originally Posted by tuxedocivic
Hi Laird. A couple question. I take it you're an MCACC user.
3. What is higher Q about it than a typical PEQ? Most PEQs can go to 5.0 or even higher. I doubt higher is ever needed for a room mode. Hence, nothing special MCACC is doing here.
Most notch filters go much higher than 5.0. They are used for specific, very-narrow-band EQ to control resonance and feedback problems. Don't underestimate the impact of standing waves either. Stop thinking "dedicated home theater" and think "family room" - with hard walls and a hard ceiling. You can end up with some really significant resonance in such an environment.
Notch filters are extremely common in live gear, and are pretty easy to program. I don't know for a fact that the MCACC correction is actually a notch - but that would be the right type of EQ to use for controlling standing waves, since the frequencies involved are very narrow band and often need significant attenuation to control. You want narrow band specifically BECAUSE you want to minimize their impact on the overall frequency profile. You use a traditional EQ to change the shape of a system's frequency profile. You use a notch filter to "knock out" specific frequencies WITHOUT having a significant impact on the rest of the overall profile. They are certainly using it like a notch filter. It would be rather foolish to do otherwise.
Originally Posted by tuxedocivic
4. Do you have any data or measurements showing that this feature is actually manipulating the IR? Are you sure the change you're hearing is what the white paper is suggesting? I'm perplexed how a microphone at the LP can do such a thing and I'm perplexed how a passive speaker can altered in such a way by dsp. If it can do what it's saying, I'll be looking to change receivers. That's major stuff there.
They are not altering the speaker. They have the output that was sent to the speaker. The mic gives them the output that came FROM the speaker. The algorithm compares the two to find where the phase shifts occur, and then uses a heuristic method (as described in a little more detail in the later pages of the marketing paper) to fit a pre-programmed phase "correction" profile to the system. When "Full Band Phase Control" is on, it applies that profile as pretty much the last step before going to the DAC. When "full band phase control" is off, the profile is not applied. It does not need to use the mic again unless you change speakers - so the determination and curve fit (which are computationally-intensive) are not being done in real-time - only the application of the fitted "correction" profile.
It is an extremely easy feature to isolate and test - since it is one of several parts of MCAAC that can be independently turned on and off in real-time while listening - from an iPad in another room. I have come about as close as i can get with my rig to running double-blinds with a couple dozen guests and the impact is pronounced. Skype texting from the iPad to their phones to ask the "optometrist question" ("This, or this?") while toggling (or not) the state of the Full Band Phase Control as they listen. The material is almost always multi-channel music in a wide range of genres (everything from Elgar and Debussy to Pink Floyd and Porcupine Tree).
I don't have the gear that would be needed to measure the audible speaker output beyond having a decent dB meter (so at least I can control for volume in my experiments) and a real-time spectrum analyzer in my phone - which is a fun toy, but since I have no confidence that the software is in the least bit calibrated to the mic on the phone, it is kind of useless.
Whether the "compensation" that is applied to the signal before it goes to the speakers is "accurate" and actually results in superior phase alignment, I cannot say for certain - although I have no reason to disbelieve Pioneer in this case. Indirect evidence is the superior imaging on my system when FBPC is turned on. As imaging is one of the first things that goes to heck when phase alignment is off-kilter...
I can say that there is a huge difference in the sound on my system just from toggling FBPC on an off, and that the sound is vastly superior with it turned on, and that the other listeners to my system agree rather enthusiastically.